Apparatus and process for the separation of liquids and solids

ABSTRACT

A liquid solid separation apparatus having a porous metal pipe sealed inside a non-porous metal pipe which allows a portion of the liquids, e.g., hydrocarbons and water to pass through the first pipe into the non porous pipe from which they are removed while solids are retained within the porous pipe. In the process there is a system pressure which aids in the filtration and a circulating velocity which removes the detained solids. Preferably a portion of these solids with reduced liquid content are recycled back to the system, mixed with fresh feed. By recycling a porion of the recovered solid concentrate the velocity of the flow in the system kept constant and the system itself is stabilized.

This is a continuation, of application Ser. No. 09/015,167, filed Jan.29, 1998 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and process for separatingsolids, particularly small particulates such as fines fromhydrocarbon/water mixtures and in the further separation of hydrocarbonand water.

2. Related Art

Some hydrocarbon streams are contaminated with particulate solids. Forexample, hydrocarbons recovered in soil reclamation under the super fundproceedings. Other examples of hydrocarbon streams which may becontaminated with particulate solids are those recovered in remediationof drilling muds, spent motor oils and the like. Shale oil and oil sandhydrocarbons may also contain small solid particles.

The solid particles are usually in the range of 0.1 micron up to 20 andare not easily separated by gravity settling but tend to stay suspendedin the hydrocarbons.

SUMMARY OF THE INVENTION

The present invention provides an apparatus and process for separatingparticulate solids from hydrocarbon stream in a continuous process bypressure filtration of the liquids and cross flow removal of theseparated solids from the filter medium.

Briefly, the present apparatus uses a porous metal pipe sealed inside anon-porous metal pipe which allows the liquids, e.g., hydrocarbons andwater to pass from the first pipe in to the second pipe from which theyare removed while solids are retained within the first pipe. There is asystem pressure which aids in the filtration and a circulating flowwhich removes the detained solids and preferably recycle a portion ofthese solids (having greatly reduced liquids content) with fresh feedback to the system.

The cross flow of the circulating flow prevents buildup of the filteredsolids. The hydrocarbons are removed from the chamber formed by theouter pipe. If water is present, the hydrocarbons and water areseparated in the outer pipe chamber by decanting, for example, with abottom drain for the water and an upper drain for the hydrocarbons.

The term hydrocarbons as used herein includes other organic compoundssuch as nitrogen, oxygen, sulfur or metal containing organic compoundsfrequently associated with hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of one embodiment of the presentinvention.

FIG. 2 is a cross section taken along line 2—2 of FIG. 1.

FIG. 3 is a cross sectional representation of a multiple porous tubeconfiguration.

DETAILED DESCRIPTION

Generally, the porous metal component is formed from non-sphericalparticles which have an irregular shape. These metal particles shouldhave a particle size from 30 to 100 micrometers with from 30 to 40micrometers being the preferred range. The porous metal component shouldhave pore sizes from 0.5 to 10 micrometers with from 0.5 to 5micrometers being the preferred range. Generally the porous metalcomponent will have a porosity of 5 to 20% prior to treatment with themetal oxide.

The porous metal component should be formed of a metal which is notcorroded by the fluids with which it is intended to be used. Generallyaustenitic stainless steels are preferred. The particularly preferredstainless steels are the 300 series with 316L being especiallypreferred.

Preferably the porous metal component in the form of a tube or pipe iscoated on the internal surface with a sintered metal oxide.

The metal oxide particles are generally spherical in shape and have aparticle size of from 0.2 to 1.0 micrometer. The metal oxide should besinterable at a temperature below the melting point of the metal used toform the support. Generally the metal oxide should coalesce at below1200° C. with from 900° to 1200° C. being the preferred range. Thepreferred metal oxide is titania. The anatase crystalline form oftitania which is converted to the rutile crystalline form upon beingheated and sintered together has given particularly good results. Fortitania the sintering temperature should be from 900° to 1200° C. withfrom 1050° to 1200° C. being preferred.

Preferably the particles removed are larger than about 0.05 micron,preferably about 0.1 micron or larger. Solids larger than about 10 maybe more easily removed by other means.

The system is preferably pressured to operate at 10-600 psi. Thetemperature of the treated materials is adjusted to facilitate thepassage of the hydrocarbon through the pores of the substrate and anymetal oxide coating by reducing the viscosity. Temperatures in the rangeof 60-300° F. are preferred. The pressure and temperature can beadjusted relative to each other to obtain optimum flow.

An important aspect of the process is the velocity of the materialthrough the inner tube(s) or pipe(s). High velocity removes the solidsfrom the porous metal tube wall and prevents plugging of the pores. Thevelocity of the feed and recirculation material is that sufficient toremove the solids from the inner tubes(s) or pipe(s), preferably about10 to 20 feet per second. The preferred velocity is 15 feet per secondof the material in the system, i.e., fresh feed and recirculatedmaterial passing through the porous inner tube(s) or pipe(s). Feed rateof material to the circulating system may range from 1 to 2100 gallonsper minute.

The apparatus is comprised of one or more, preferably multiple, porousmetal tubes and more preferably a plurality of such tubes runningthrough and enclosed by a non-porous container, e.g., a larger pipewhich forms a chamber to receive the filtered liquid.

A preferred system is comprised of one or more stainless steel tubes6-75 mm in diameter with a TiO₂ coating sintered to the inside diameterTypically the tubes are welded together into an all stainless steelmembrane module. One or more modules may be connected in series orparallel.

The hydrocarbon feed material may contain water in addition to the solidparticles. Up to 25 vol. % water may be present in the fresh feed.

Referring now to FIG. 1 a particular embodiment is illustrated as aschematic flow diagram. A hydrocarbon material containing particulatesolids preferably in the range of 0.1 to 20 microns is accumulated in afeed tank 10 from which it passes via line 12 to feed pump 14 whichserves to pressurize and supply feed to the system. From the feed pumpthe pressurized feed passes via line 16 to circulation pump 18 whichmaintains the velocity of the material flowing through the separatingzone. The feed enters the separating zone through line 20. In thisembodiment the separating zone is comprised of multiple sections, 22 a,22 b, 22 c and 22 d, arranged in series. section 22 a, the hydrocarbonfeed flows through porous metal tube 40 a, where a portion of theliquids in the feed (hydrocarbons and optionally up to about 0-25 volpercent water) pass through porous tube 40 a into the chamber 21 aformed by tube 22 a surrounding porous tube 40 a. The porous tube mustbe enclosed by an outer non-porous tube or some equivalent structure tocreate a chamber to receive the permeated liquid. The permeated liquidis collected in the chamber 21 a and exits via line 36 a.

In a similar manner the feed stream flows out of section 22 a throughregular non-porous conduit 24 into section 22 b where a further portionof the liquid permeates porous metal tube 40 b into chamber 21 b fromwhich it passes via line 36 b. From section 22 b via line 26 the feedstream passes to section 22 c where a further portion of the liquidpermeates porous metal tube 40 c, is collected in chamber 21 c andremoved via line 36 c. The material in section 22 c passes vianon-porous tube 28 to section 22 d where a final portion of the feedliquid passes into chamber 21 d and is removed via line 36 d. Eachpermeate removal line feeds to a single line 38 for recovery.

The solid concentrate exits the treatment separating zone via line 30from which it may be removed from the system through valve 34 and line36 or all or a portion may be returned to the hydrocarbon feed to theseparation zone. Alternatively the recycled concentrate may be returnedto the feed tank via line 42. The recycle concentrate is considered asfeed component for determining the necessary feed velocity through thesystem and is used to keep the feed at a constant solids density abovethe source hydrocarbon, thereby optimizing the system and allowingconstant operating conditions for the most economic and effectiveoperation. Any number of porous metal tubes may be positioned within achamber and any number of sections may be arranged in series in theapparatus to achieve the degree of separation desired.

The concentrate may be used as bunker fuel or in the case of ahydrocarbon source derived from a remediation system, the concentratemay be returned to the remediation system. If the permeate recovered vialine 38 contains water, the stream may be sent to a distillation unit(not shown) or decanter (not shown) to separate water and hydrocarbons.

FIG. 3 illustrates an embodiment which is particularly useful forhydrocarbon/water/solid streams. There are four porous metal tubes, 60a-60 d, positioned within non-porous tube 60 either in a system as shownin FIG. 1 or other configuration. The hydrocarbon and water permeate theporous tubes and water is removed via line 66 while hydrocarbons areremoved from chamber 63 via line 64.

EXAMPLE

The source feed was derived from a hydrocarbon vapor recovery systemused to purify vapor from a drilling mud remediation in which dieselboiling range material used as a component of the drilling mud. Thesource hydrocarbon feed had the characteristics shown in the TABLE.

TABLE Hydrocarbons 85 Vol. % Water  5 Vol. % Solids 10 Vol. % Particlesize range .1 to 20 microns

In an apparatus arranged similarly to that illustrated in FIG. 1, thesource feed was pumped from the feed tank into the separation zone at apressure of 25-300 psig, temperature of 150° F. and at a rate of 5-10gpm. Each section of the separation zone comprises four 5 ft. long,{fraction (1/2 )} inch ID stainless having titanium dioxide internalcoating and positioned centrally as shown in FIG. 3 and sealed inside a5 ft. long, 2 {fraction (1/2 )} ID stainless steel pipe. A portion ofthe solid concentrate was recycled to the feed line, as required, tomaintain the system velocity.

The invention claimed is:
 1. An apparatus comprising: a non-porous tube,at least one porous metal tube comprising stainless steel, having a poresize in the range of 0.5 to 10 micrometers, being coated internally withsintered metal oxide, positioned in said non-porous tube, and sealedwithin said non-porous tube, said non-porous tube having an upperportion and a lower portion; at least one line for continuous use toremove a first liquid from the apparatus and connected to the upperportion of said non-porous tube; at least one line for continuous use toremove a second liquid from the apparatus and connected to the lowerportion of said non-porous tube; a feed line connected to said tubularporous metal tube, a solids removal line connected to porous metal tubedistal to feed line; a circulating cross flow pump operably positionedon the feed line; a feed tank upstream of said cross flow pump andconnected to said feed line; and a second pump in said feed line topressurize the feed, said solids removal tube being connected to saidfeed tank.
 2. The apparatus according to claim 1 wherein said metaloxide comprises titanium oxide.
 3. The apparatus according to claim 4wherein said pore size of said combined porous metal tube and sinteredtitanium oxide is in the range of about 0.5 to about 0.01 microns. 4.The apparatus according to claim 1 wherein said pore size of said porousmetal is in the range of 0.5 to 5 micrometers.